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See Dev.java for updated tutorials taking advantage of the latest releases.
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Historically, an Internet ___domain name contained ASCII symbols only. As the Internet gained popularity and was adopted across the world, it became necessary to support internationalization of ___domain names, specifically to support ___domain names that include Unicode characters.
The Internationalizing Domain Names in Applications (IDNA) mechanism was adopted as the standard to convert Unicode characters to standard ASCII ___domain names and thus preserve the stability of the ___domain name system. This system performs a lookup service to translate user-friendly names into network addresses.
Examples of internationalized ___domain names:
If you follow these links you will see that the Unicode ___domain name represented in the address bar is substituted with the ASCII string.
To implement similar functionality in your application, the java.net.IDN class provides methods to convert ___domain names between ASCII and non ASCII formats.
| Method | Purpose |
|---|---|
|
toASCII(String) toASCII(String, flag) |
Used before sending an IDN to the ___domain name resolving system or writing an IDN to a file where ASCII characters are expected, such as a DNS master file. If the input string doesn't conform to RFC 3490, these methods throw an IllegalArgumentException. |
|
toUnicode(String) toUnicode(String, flag) |
Used when displaying names to users, for example names obtained from a DNS zone. This method translates a string from ASCII Compatible Encoding (ACE) to Unicode code points. This method never fails; in case of an error the input string remains the same and is returned unmodified. |
The optional flag parameter specifies the behavior of the conversion process. The ALLOW_UNASSIGNED flag allows including code points that are unassigned in Unicode 3.2. The USE_STD3_ASCII_RULES flag ensures that the STD-3 ASCII rules are observed. You can use these flags separately or logically OR'ed together. If neither flag is desired, use the single-parameter version of the method.